During the previous funding period, we completed a series of studies that assessed the capacity of patients with temporomandibular disorders (TMD) to process nociceptive stimuli. We established that TMD patients who have muscle pain (myalgia) with or without joint pain (arthralgia) exhibit enhanced perceptual responses to quantitative noxious stimuli compared to age-and gender-matched controls. Although these findings are interesting, they are based on case-controls studies and thus have not adequately established a potential causal relationship between pain sensitivity and the development of TMD. We propose a series of studies that more fully characterize the relationship between pain sensitivity and factors influencing pain sensitivity (i.e., menstrual cycle resting arterial blood pressure, psychosexual factors), with the likelihood of developing painful TMD. The goals of this subproject are: 1) to conduct a three year prospective study that determines whether pain sensitivity, assessed with an ischemic pain task, as a risk factor which contributes to the development of painful TMD within a cohort of initially symptom-free females aged 18-34 year; 2) to determine if TMD onset and ischemia intolerance either alone or in combination, are associated with anatomically non-specific enhancement of thermal-and mechanical-pain sensitivity of thermal-and mechanical-pain sensitivity and, if so, to evaluate if anatomically non-specific pain sensitivity is a risk factor for TMD onset; 3) to determine if TMD onset and ischemia intolerance, either alone or in combination, are associated with enhanced C-fiber mediated pain and, if so, to evaluate if C-fiber mediated pain is a risk factor for TMD onset; 4) to determine if TMD onset and ischemia intolerance, either alone or in combination, are associated with more frequent and severe menstrual cycle complaints and, if so, to evaluate if menstrual cycle complaints are a risk factor for TMD onset; 5) to examine relationships between TMD onset, ischemia intolerance and various psychosocial measures. The outcomes of these studies will provide a greater understanding of putative risk factors that contribute to the development of TMD and will assist in develop rational theory-based approaches for the treatment of these common and potentially disabling disorders.